[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] espfix/xen: Fix allocation of pages for paravirt page tables
On Wed, Jul 09, 2014 at 01:18:18PM -0400, Boris Ostrovsky wrote: > init_espfix_ap() is currently off by one level when informing hypervisor > that allocated pages will be used for ministacks' page tables. > > The most immediate effect of this on a PV guest is that if > 'stack_page = __get_free_page()' returns a non-zeroed-out page the hypervisor > will refuse to use it for a page table (which it shouldn't be anyway). This > will > result in warnings by both Xen and Linux. > > More importantly, a subsequent write to that page (again, by a PV guest) is > likely to result in fatal page fault. > > Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> <sigh> > --- > arch/x86/kernel/espfix_64.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kernel/espfix_64.c b/arch/x86/kernel/espfix_64.c > index 6afbb16..94d857f 100644 > --- a/arch/x86/kernel/espfix_64.c > +++ b/arch/x86/kernel/espfix_64.c > @@ -175,7 +175,7 @@ void init_espfix_ap(void) > if (!pud_present(pud)) { > pmd_p = (pmd_t *)__get_free_page(PGALLOC_GFP); > pud = __pud(__pa(pmd_p) | (PGTABLE_PROT & ptemask)); > - paravirt_alloc_pud(&init_mm, __pa(pmd_p) >> PAGE_SHIFT); > + paravirt_alloc_pmd(&init_mm, __pa(pmd_p) >> PAGE_SHIFT); > for (n = 0; n < ESPFIX_PUD_CLONES; n++) > set_pud(&pud_p[n], pud); > } > @@ -185,7 +185,7 @@ void init_espfix_ap(void) > if (!pmd_present(pmd)) { > pte_p = (pte_t *)__get_free_page(PGALLOC_GFP); > pmd = __pmd(__pa(pte_p) | (PGTABLE_PROT & ptemask)); > - paravirt_alloc_pmd(&init_mm, __pa(pte_p) >> PAGE_SHIFT); > + paravirt_alloc_pte(&init_mm, __pa(pte_p) >> PAGE_SHIFT); > for (n = 0; n < ESPFIX_PMD_CLONES; n++) > set_pmd(&pmd_p[n], pmd); > } > @@ -193,7 +193,6 @@ void init_espfix_ap(void) > pte_p = pte_offset_kernel(&pmd, addr); > stack_page = (void *)__get_free_page(GFP_KERNEL); > pte = __pte(__pa(stack_page) | (__PAGE_KERNEL_RO & ptemask)); > - paravirt_alloc_pte(&init_mm, __pa(stack_page) >> PAGE_SHIFT); > for (n = 0; n < ESPFIX_PTE_CLONES; n++) > set_pte(&pte_p[n*PTE_STRIDE], pte); > > -- > 1.8.1.4 > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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